High pH and green water

[twinmomma]

I have also posted this on the Pool Algae forum.

Please help, I am VERY frustrated. We have been battling High Ph for several weeks and the level is not decreasing. Our pool water is now green.

We had the water tested yesterday:
Temp - 84
CYA 151
Total Chlorine 6
Free Chlorine 6
pH 7.8
Total Alkalinity 130
Adj. Total Alkalinity 85
Total Hardness 219

OUt pH was 8.2 as of 7/22. We added 3.5 lbs of pH Decreaserand clean shock. On 7/24 we were told to add 2.5 lbs of pH decreaser and 3 lbs of clean shock. Yesterday we were told to add 4 lbs of decreaser and 2 lbs of SOS. Yesterday afternoon the water looked as if it had lost some of its green color. Today it is the greeenest it has been.

We have an 18,000 gallon above ground pool. Any advice you can give is greatly appreciated.

Thanks.

[lbridges]

I recommend you plug your numbers into the pool calculator.

Your CYA value at 151 means the FC will have to be much higher to kill off and then avoid algae in the future. Before adding more shock/chlorine to the pool make sure you're adding it in liquid bleach of 12% chlorinating liquid since Trichlor (tabs) and Dichlor both will keep raising the CYA number and continue to make it harder to avoid algae.

[twinmomma]

Thanks for the reply. I'll try adding some liquid bleach.

I must say, I am confused because the pool store told me that I had to get my pH down before anything else will work and the decreaser has not been decreasing the pH. I thought about going out and buying some muriatic acid. They told me that while my pH was high the chlorine would not work. However, everything I am reading, if I understand it correctly, tells me that I need a high level of chlorine to kill the algae and get the water clear again. I am so confused.

I am going to try the pool caclulator. Thank you so much for directing me to it. This is our 2nd summer for the pool. Last summer we didn't have any issues but it was a cool summer. This summer has been HOT and I'm thinking that may be part of our problem.

Thanks again!

[lbridges]

First, I wouldn't trust the pool store. Many are poorly trained and nobody will care like you do.

I would guess a bit less than 1/2 gallon of muratic acid would take you down to the median pH values.

If your pH is 7.8 then that is at the high end of OK, but not dangerously so, and it's OK to add bleach or chlorinating liquid. More than a few people who use salt water pool equipment to generate chlorine safely keep their pH around 7.6 to 7.8.

[chem geek]

If you are going to shock to high levels, it is better to get the pH down to 7.2 before adding the chlorine. Adding bleach or chlorinating liquid will raise the pH and at shock levels it does so quite a bit. For lowering the pH, Muriatic Acid won't add unnecessary sulfates that come with dry acid, but it is nasty stuff (the half-strength Muriatic Acid doesn't fume quite as much).

[twinmomma]

Thanks Chem Geek.

Does it seem "normal" that I have added so much pH down and th pH is not decreasing?
Should I use the muriatic acid vs the dry acid?

I need to go and get a new read out today,I am hesitant to go back to the pool store.

The pool is still green this morning.

[chem geek]

When the TA is on the high side, the pH will tend to rise due to carbon dioxide outgassing. Remember that shocking is not a one-time event -- it is a SUSTAINED high level of chlorine and you'll need to add chlorine frequently at first as the chlorine will get consumed killing algae. I recommend you read the Pool School, especially the article on Defeating Algae.

[twinmomma]

Ok - yesterday I added 1 gal of Muriatic Acid and my pH was low this morning. We added a total of 9 gal of liquid bleach today and the water is still green this evening and my pH is around 7.5.

I hope to see an improvement in the water tomorrow. This is just so frustrating, last year was the 1st year for the pool and we had a very cool summer in Ohio and didn't get to use it much. This summer, we built a deck and the weather has been perfect. We haven't used the pool all week and have 3 weeks befroe school starts again! UGH!

[chem geek]

As was noted in earlier posts in this thread, your high CYA level is going to make it much harder to kill off the algae as it will take a very high level of chlorine to do so. You will need to lower the CYA via a partial drain/refill anyway so if you did that you would need less chlorine to fight the algae. Just remember that the chlorine level will drop fairly quickly killing the algae. You would need a FAS-DPD chlorine test kit to be able to accurately test the high level of chlorine. Personally, I would have done the partial drain/refill first.

[twinmomma]

Yippee - algae is gone. pH is low and holding. My water is now cloudy/milky. I added 2 lbs of shock and 2 clarifying tablets this morning. I'm not sure how long it will take to clear up. I'm wondering if I should add more shock?